Influence of varied dosages of nitrogen application on the leafhopper population in Bt cotton under rainfed condition

摘要

Field experiments were carried out to study the influence of nitrogen dosages (0, 25, 50, 75, 100, 125, 150, 175 and 200 kg/ha) on cotton leafhopper population under rainfed condition in Dharwad during 2011-12 and 2012-13. Mean population of leafhopper was highest at higher dosages of nitrogen as compared to recommended and lower dosages of nitrogen. A positive and significant correlation between the insect-pests and nitrogen fertilizer was observed. Leaf nitrogen content increased with the increasednitrogen dosages applied wherein leafhopper population correlated positively and significantly with the leaf nitrogen content. Increased levels of nitrogen from 0 to 125 kg/ha significantly increased production of good opened bolls per plant, total bolls per plant and seed cotton yield. Further increased level of nitrogen from 150 to 200 kg/ha increased leafhopper population and reduced the seed cotton yield.